1. Field of the Invention
The present invention relates to the field of signal processing and, more particularly, to the compression and expansion of audio signals.
2. Prior Art
In the processing of audio information, compression and expansion techniques are utilized in order to speed the rate of transfer of the information, as well as reducing the amount of required memory space for storing the information.
Audio compression techniques decrease the amount of memory space required to store digitized audio information. It is to be noted that digitized audio information require significant amounts of memory for relatively short amount of recorded or play time. This requirement for large amounts of memory increases significantly when the audio information being stored is to have a quality equivalent to high fidelity music. For example, in one particular application, one minute of digitized audio speech requires approximately 0.5 megabytes of memory. However, when the digitized audio to be stored is to have a compact disc (CD)-quality for storing music, one minute of digitized music may require in the order of 5.3 megabytes. Thus, approximately ten times the memory space is required to store one minute of digitized CD quality music as compared to ordinary telephone-quality speech.
In order to store high fidelity (i.e. CD-quality) music, very large amounts of memory space is required to store the information. In order to reduce the required memory capacity, various audio compression techniques have been devised in order to compress the digitized audio information prior to storage. Audio expansion techniques are then utilized to retrieve the compressed data and expanding such data in order to reproduce the original audio for playback.
However, it is critical that the compression technique used does not lose or distort the original information appreciably. Further, the audio expansion technique used should also be capable of reproducing the originally stored music. Thus, an audio compression/expansion technique for storing high fidelity music must be capable of reducing the required memory capacity, but at the same time be capable of reproducing the original sound without appreciable loss or distortion.
Additionally, where such high fidelity music is to be processed at real-time, especially for playback, it is essential that the compression and expansion techniques not be overly complicated so that the data can be processed and stored, and later retrieved and processed for reproduction at real-time speeds.
It is appreciated that the audio compression/expansion techniques of the present invention processes and stores high fidelity music, and retrieves and reproduces such stored music at real-time speeds.